Manufacturers of distributed process control systems design their control systems to be used with a variety of industrial processes. For example, the general hardware and software that a distributed process control system manufacturer may create may be used in such diverse applications as running a power plant to controlling a food processing facility. For this reason, the manufacturers of the distributed process control systems intentionally create their systems to be easily adaptable to a plurality of different controlled processes.
However, there are niche markets in the process control realm for which general process control systems are not particularly suited. For example, the measurement of the flow of hydrocarbons (e.g., natural gas, liquefied natural gas, oil, gasoline) for purposes of custody transfer is a niche market for which the general tools provided in a distributed process control system are inadequate. Stated otherwise, while some distributed process control systems may have function blocks to perform flow measurement calculations, the flow measurement calculations provided are not of sufficient accuracy for custody transfer (i.e., billing) purposes. Moreover, many legal jurisdictions have regulatory audit requirements regarding the measurement of the flow of hydrocarbons, and the general tools for flow measurement calculations of process control systems do not meet such requirements. As yet another example of a niche market for which distributed process control systems are not particularly suited is turbine (e.g., gas turbine, steam turbine) control. Turbine control system control not only control valve position for turbine speed/load control, but also implement various specialty functions like heat soaking a turbine for proper expansion of the various components after periods of inactivity, and in the case of gas turbines fuel flow control. As yet another example of a niche market for which a distributed process control systems are not particularly suited is hydrocarbon quality monitoring (e.g., BTU content, hydrocarbon makeup, entrained liquid in natural gas flow), and some legal jurisdictions also have specific metrological requirement regarding quality monitoring.
Because of the complexity and requirements regarding specialty systems, such as metering of hydrocarbons for custody transfer, turbine control, and hydrocarbon quality monitoring, in the related art the specialty systems are a separate physical systems.